Several studies, including those of B3OA, have demonstrated the ability of mesenchymal stem cells (MSCs) seeded on a porous scaffold to repair large bone defects. The reproducibility of this method, however, is mediocre and, most importantly, lower than the one of the autograft, which remains the gold standard for bone repair. Several causes may explain these unsatisfactory results including non-optimized material scaffold and/or non-optimized cellular preparation. A major challenge is to increase the survival and functionality of implanted MSCs so that they promote more potently the new bone formation. Several strategies are being developed by the B3OA:
1- Increasing MSC survival using glucose delivery
This limited success may be caused by the massive cell death observed after MSC transplantation, with 80-90% of cells dying within the first days. This death might be explained by the fact that the cells are transplanted in an ischemic environment (deprived of oxygen and nutrient), caused by the absence of vascularization in the bone defects. The lack of oxygen was thought to be the most detrimental factor for MSC survival and function. Recent work from the B3OA, however, is questioning this paradigm: glucose (main nutrient for cell metabolism) appears to also play a critical role in MSC survival in an ischemic environment. The addition of exogenous glucose, indeed, allows MSC to survive even in a near anoxic environment (complete deprivation of oxygen).
These findings improve our knowledge of the mechanisms involved in MSC death after transplantation. Based on this better understanding, the B3OA is developing new strategies to deliver in situ exogenous glucose in order to improve post-transplantation survival and functions of MSCs. These findings are of high interest not only for bone, but also for cardiac, cartilage tissue engineering.
2- Optimizing the architecture and chemistry of scaffold materials
There are numerous biomaterials used as porous scaffolds for delivering MSCs. Calcium phosphate-based materials are among the most popular ones for filling bone defects due to their biocompatibility, chemical composition (close to the inorganic part of bone) and osteoconductive properties. However, the poor vascularization and bone ingrowth into porous scaffolds does not make them satisfactory for the repair of large bone defects. Novel materials must display additional properties, they especially must promote bone formation in the core of implants. For this, the intrinsic properties of the materials must modulate the functionality of bone cells (including both resorption cells (osteoclasts) and forming cells (osteoblasts and MSCs). A collaborative project with the Center for Biomedical and Healthcare Engineering / Sainbiose in Saint-Etienne aims to optimize the physico-chemical and/or architectural properties of bone substitutes in order to enhance the repair potential of bone tissue engineered products.
Thanks to computer-aided design and new additive manufacturing technology it is now possible to produce implants with complex customized external shapes as well as optimized and reproducible internal macro-architecture (e.g., pore interconnectivity, shape, size and distribution) that promote cell and tissue invasion and nutrient transport. One of our objectives is to determine the internal architectures most advantageous for the survival of MSCs within the scaffold and/or for the osteo- and angio-conductive properties of the scaffold. In addition, we assess “biomimetic” materials, i.e. with characteristics closer to the biological bone apatite, in particular by doping the apatite crystal lattice with ions of biological interest. The aim of this work is to acquire a better understanding of the influence of the physico-chemical and architectural parameters of these materials on the biological responses involved in the bone repair.
Publications of the project
Salazar-Noratto GE, Luo G, Denoeud C, Padrona M, Moya A, Bensidhoum M, Bizios R, Potier E, Logeart-Avramoglou D, Petite H. Understanding and leveraging cell metabolism to enhance mesenchymal stem cell transplantation survival in tissue engineering and regenerative medicine applications. Stem Cells. 2020 Jan;38(1):22-33. Link for the publication .
Moya A, Paquet J, Deschepper M, Larochette N, Oudina K, Denoeud C, Bensidhoum M, Logeart-Avramoglou D, Petite H. Human Mesenchymal Stem Cell Failure to Adapt to Glucose Shortage and Rapidly Use Intracellular Energy Reserves Through Glycolysis Explains Poor Cell Survival After Implantation. Stem Cells. 2018 Mar;36(3):363-376. Link for the publication .
Moya A, Larochette N, Paquet J, Deschepper M, Bensidhoum M, Izzo V, Kroemer G, Petite H, Logeart-Avramoglou D. Quiescence Preconditioned Human Multipotent Stromal Cells Adopt a Metabolic Profile Favorable for Enhanced Survival under Ischemia. Stem Cells. 2017 ;35(1):181-196. Link for the publication .
Deschepper M, Manassero M, Oudina K, Paquet J, Monfoulet LE, Bensidhoum M, Logeart-Avramoglou D, Petite H. Proangiogenic and prosurvival functions of glucose in human mesenchymal stem cells upon transplantation. Stem Cells. 2013 ;31(3):526-35. Link for the publication .
Deschepper M, Oudina K, David B, Myrtil V, Collet C, Bensidhoum M, Logeart-Avramoglou D, Petite H. Survival and function of mesenchymal stem cells (MSCs) depend on glucose to overcome exposure to long-term, severe and continuous hypoxia. J Cell Mol Med. 2011 Jul;15(7):1505-14. Link for the publication .
Charbonnier B, Manassero M, Bourguignon M, Decambron A, El-Hafci H, Morin C, Leon D, Bensidoum M, Corsia S, Petite H, Marchat D, Potier E. Custom-made macroporous bioceramic implants based on triply-periodic minimal surfaces for bone defects in load-bearing sites. Acta Biomater. 2020 Jun;109:254-266. Link for the publication .